P7. Abstract This project aims to site-specifically characterize transient interactions between HIV-1 reverse transcriptase (RT) and its binding partners by solution NMR and to investigate the effects of such interactions on the dynamics of the interacting system. Solution NMR studies of RT and complexes thereof are challenging, given the size of the RT heterodimer. This necessitates developing and applying new methodological approaches suited for investigations of large molecular complexes. While the current RT X-ray structures provide important insights into how RT interacts with drugs and substrate, they are static snapshots of a subset of conformational states captured through crystallization. These structures do not inform on the motions within the protein or complex, which are critically connected to its functions. In this project, we will fill the existing knowledge gap and determine the functionally important dynamics in RT. Specifically, we will i) identify which domains and residues of RT are involved in the interaction with Integrase (IN); ii) delineate specifically the intermolecular contacts on RT and determine the RT/IN dynamics; and iii) determine the biological significance of structural or dynamics changes in RT upon IN and nucleic acid binding. To accomplish the specific aims of this project, we will employ a multi-pronged approach encompassing solution NMR as well as enzymology and virology studies. We will combine the complementary expertise of the PCHPI investigators and collaborators and work in close synergy to tackle the important questions concerning the role of dynamics in RT for HIV infection.